Jacquie Clermont’s desk job as a software tester for Liaison International in Watertown once left her cramped and sore.

“I used to get up and I’d be bent over and I’d say ‘ouch, ouch, ouch,’ "she recalled.

A month ago, Clermont joined a handful of co-workers who fashioned elevated desks out of cardboard boxes and wooden planks so that they can work while standing up. Since then, her back pain has disappeared.

“My focus is much better,’’ Clermont said. “I have more energy and I’m more alert.’’

Once quirky outliers in the office, employees who prefer to stand at their desks and in meetings are multiplying in corporate America - and companies that supply office goods are reporting that sales of height-adjustable furniture are up significantly.

“Sit-stand desks have moved from a niche product category to one that is standard in the top commercial furniture retailers,’’ said Ann Hall, a marketer for the Danish manufacturer Linak Group, which makes components that elevate desks. Sales of the devices have increased by triple-digits since 2000, Hall added.

“Now every major manufacturer has a height-adjustable desk. The market is booming,’’ she said.

Other makers of office furniture have added to their lines of “sit to stand’’ desks and workstations, as have office suppliers such as Staples Inc., which offers in its online store four “height-adjustable workstations, due to customer interest,’’ said Carrie McElwee, a spokeswoman.

The trend dates to the early days of the modern economy: A century ago, only managers sat; the rest of the workers stood.

“Think of the characters in Dickens’s novels,’’ said Jack Dennerlein, coprincipal at the Center for Work, Health and Wellbeing at the Harvard School of Public Health.

While standing at work was popular in Scandinavia for decades, it began catching on elsewhere in the late 1990s, with the rise of dispatch and call centers, where workers who sat for long stretches would report carpal tunnel syndrome, back ailments, and other problems.

Office workers who work standing up report improved posture, increased productivity, and a stronger body core.

In studies conducted by the Mayo Clinic and the University of Missouri, researchers found that desk workers who stood during the workday had lower levels of stress and anxiety, increased flow of blood and oxygen to the brain, and the release of endorphins.

But Dennerlein cautions that standing at work is not an easy transition for everyone.

“When you stand, you are always changing the load on your body; you sway and change your weight,’’ he said. “For an office worker, a desk is a really important tool. You need to know how to use them properly, like a carpenter with a hammer.’’

At the Newton headquarters of TripAdvisor, the online travel site, 11 percent of approximately 310 employees have ditched their chairs in favor of standing. One is vice president Cindy Roche, who propped a wooden lectern on her desk.

“It’s only in the past 100 years or so that we’ve become a culture of office sitters,’’ she said. “Standing desks feel more like a return to a better standard than an innovation.’’

The offshoot of this trend is that people are also standing more during the ubiquitous office meeting. At TripAdvisor’s weekly recruitment meetings, everyone stands, said global recruiter Jennifer Ramcharan.

“There are fewer distractions and everyone seems more engaged,’’ said Ramcharan, one of 10 employees who stood while strategizing around a whiteboard recently. “I’ve also noticed that we make eye contact with each other more.’’

While a standing desk or convertible workstation can cost two to three times as much as a conventional desk, prices have come down in recent years, making it easier for companies to justify buying new furniture.

Moreover, companies are increasingly making desks that can be used either way, sitting down or standing up.

At $1,500, the Airtouch desk made by Steelcase Inc. is a sleek, freestanding table that can go from a sitting to standing position in less than two seconds with a lift handle. The Grand Rapids, Mich., furniture maker said sales of adjustable desks are growing at three times the rate of general furniture.

And for the more adventurous, there are so-called treadmill desks, which are elevated workstations that allow workers to exercise on the built-in treadmill. Recently Blue Cross Blue Shield of Massachusetts spent more than $20,000 for six of them for its Boston, Quincy, and Hingham offices.

Employees have to sign up for the treadmills - at one-hour increments - and Blue Cross officials said there are waiting lists to use them.

Elyse Blanda, a contract specialist, tried the treadmill desk recently at the Blue Cross Boston office and liked it so much she has been on it frequently.

The treadmill goes no faster than 2 miles an hour. Blanda said she uses the time to check e-mail and review documents while burning a few extra calories.

Manufacturers such as Steelcase and Trekdesk, an Arizona company that makes desks to fit around treadmills, say corporate and home office sales are rising.

“I was skeptical at first that it would become distracting,’’ said Sherry Pagoto, an associate professor of medicine at the University of Massachusetts Medical School in Worcester, who spent $600 to turn her treadmill into a workstation.

But since stepping on in January, just the opposite has happened. “I don’t get stir-crazy, sleepy, or drowsy,’’ she said.

Some companies have found that standing up has spawned other health or fitness actions in their offices.